Change display of User dropdown to Name + Email

[brianhogg]

Is your feature request related to a problem? Please describe.
Currently the dropdown for users, such as enrolling a student in a course, is "username ". This isn't always clear since the email may not match the name of the student, making it more difficult to find.

Describe the solution you'd like
Show "name " in the dropdown instead. Also try to make it so searching will search by name and not just username or email.